I don't recall reading about guns in the USA constitution, but anyway. lol

For what purpose? To shoot people right? In so-called self-defense? That's still the old Western John Wayne way of thinking.
It's that way of thinking of feeling as though MUST own a gun. Feel empty & defenseless without one.
If the control over guns & their removal from 'everywhere' was carefully done as in other countries, then no need for one.
If the so-called threateners do not have a gun, then why should anybody else have one? Gun for self-defense in that scenario is ridiculous, overkill to say the least. It would be giving the defensee the same 'POWER' thinking in their mind as the invader if they had a gun. The old western shootout thinking & bluffing. If the invader did not have a gun, why would the defensee feel the need for one? POWER gone to the head? Amazing what a gun in the hand does to ones mind hey!

So how do you remove the guns off the streets, out of the hands of the common criminals? A long hard trek but it's mostly do-able. Sure, like UKBob's link suggests, there's always the heavier crime figures who find some way of obtaining them.

Per head of population, the gun deaths in USA compared to other countries in the world is quite amazing. Short notice so I haven't sought to re-find such figures. Perhaps you can search yourself.
The latter. A conman; deep down knowing. He was selling to crime gangs &/or gun dealers so knew what he was doing & what the guns would most likely be used for. IMHO